Expression of hup Genes in Azorhizobium caulinodans and Their Coregulation With RuBP Carboxylase

In Azorhizobium caulinodans strain IRBG 46, H₂ evolved by nitrogenase induced uptake hydrogenase ex-planta. The strain expressed an efficient H₂ recycling system under both symbiotic and ex-planta conditions. For the first time, a comparable relative efficiency of electron transfer to N₂ via nitrogenase under symbiotic as well as ex-planta conditions for both Hup⁻ strain B11 as well as Hup+ strain IRBG 46, has been reported. The study also suggested a coordinate regulatory relationship between rublsco and hup genes.